I had this issue in my 04 Laramie with Infinity system, but I had replaced the factory stereo with a double din pioneer and used a harness to bypass the factory amp for door and dash speakers. Then I modified the doors to fit 1ohm Infinity Kappa 6x9's and 6.5's. Then I ran the 5v pre-amp to a Fosgate Punch 1000w amp powering two 12" Fosgate Punch subwoofers in a Fox box underneath the rear seats.
So I was thinking it was an issue with the grounding.. to replace all that and still have the issue.
**On a side note, though, I did notice that it doesn't fade in and out at higher volumes. I also noticed that it'll fade in or out when hitting a bump or pothole. So. I discovered that if I smack the dash above the radio.. it'll fade it back in. Just doesn't stay that way.
Anyways it's been the best damn truck I've ever had. It just passed 300k miles and still runs like brand new.
So I went out last week and bought a 2010 Laramie with only 50k miles. Still has that new car smell. All factory.. music does the same thing. The thing is.. it didn't start doing it until today, which is why I'm here, after I adjusted the equalizer settings in the radio to "Bass -2, Mid +0, High +2"
I thought, "Maybe the factory amp doesn't like when you play with the equalizer l, fade and balance.." but the factory amp was bypassed in the 04.
Now.. I'm no certified technician, but I am very familiar with electronics on general and it still seems to me like a grounding issue. A weak ground would cause issues that a diagnosis test may read as being a component issue while it's actually just being affected by the problem source, in my opinion.
That technician told the other poster his issue was the factory amp. I'm looking at the 04 thinking it's issue is the stereo ground. Not necessarily a loose ground, but perhaps an insufficient wire gauge.
What I'm going to try.. is to run an additional ground wire from the battery to the frame, then run a new ground to the stereo.. and see if that makes a difference. There's way too many electronics in these trucks to be skimping out on the grounding anyways.
I'll post if that fixes it.